The complete amino acid sequence of human A-I has been determined. A-I is a 243 amino acid single chain protein containing no carbohydrate or disulfide bridges. A-I contains no long segments of hydrophobic residues, and the lipid binding properties are related to the secondary, tertiary and quaternary structure of the proteins. ApoD, an apolipoprotein recently proposed as a cofactor for lecithin cholesterol acyl transferase, has been isolated and characterized. Purified apoD is a single band on SDS electrophoresis, and the amino acid composition and immunological properties have been determined. A new large scale sequencer cup for automated Edman degradations has been developed. With this new method, the length of degradation on a single sequencer run has been extended 2 fold, and the ability to sequence large proteins (greater than 250 residues) has been significantly improved. BIBLIOGRAPHIC REFERENCES: Osborne, J.C. Jr. and Brewer, H.B. Jr.: Plasma lipoproteins. Adv. Prot. Chem. 31: 253-337, 1977. Brewer, H.B. Jr. and Bronzert, T.: Human plasma lipoproteins. Fractions 1: 1-11, 1977.